There is a container which comprises a collapsible and removable side walls and a base connected to the side walls, such connection generally in forms of a hinge. A small door may be provided on a side wall, which is used to reach the interior of the container without having to open or disassemble the whole side wall. Such container is well known, especially a large container used for transport and storage of various objects, such as a single object or bulk material. Such container may be folded when it is empty, so that the height of the container considerably shorter, the occupied space is largely reduced so as to be shipped back for re-loading. Further, one or more side walls may be removed for replacing with a new one. Moreover, it is convenient for user to pick up goods from the bottom of the container when a side wall is provided with a small door.
Usually, the side walls are hinged at its lower end to the base of the container using hinges, and the small door is hinged to the side wall by a hinge too. By rotation around the hinge, the side walls may switch between an upright position and a lying down position. The small door in the side wall also be opened and closed by rotation of a hinge.
When using the container, the side walls of the container needs to be remained upright and the small door needs to be kept closed, thus a locking means is needed to hold them in a desired state.
To achieve the above object, an engagement structure is provided between the adjacent side walls, which lead to partly locking the adjacent side walls. If the adjacent side walls are further locked, each side wall may remains upright which is required when used. The usual practice is to provide a groove on a side wall, the groove being close to the edge of the side wall and close to an adjacent side wall. A latch is positioned in the groove, and a recess is provided on the adjacent side wall so as to accommodate the end of the latch. The side walls may be locked or unlocked by making the latch enter or leave the recess.
U.S. Pat. No. 4,923,079 discloses a typical push-pull locking system. The patent discloses a groove on a side wall and a recess on an adjacent wall. The latch may enter the recess through the groove. Further, a spring means is provided to reset the latch and keep the latch in a locked state. When people push or pull the latch away from the recess, the side walls are unlocked, and the side walls can be folded. Similarly, the locking system may also suitable for the small door.
The above method is a very easy way to achieve mutual inter-locking side walls, however, it is difficult when operating the latch.
WO2005102852 discloses a typical rotary locking system. It is mainly characterized in that the latch having a pivot perpendicular to the side wall, when rotate the latch, the end of the pivot enters into or leaves a groove of the adjacent side wall. The latch further includes an elastic blade, so as to drive the latch reset and remain locked.
The patent effectively reduces the force needed to unlock, but it has a certain degree of complexity in the assembly. Further, it has a limited locking strength.